Did you actually read the report that the CMA released?
They are not basing the block on some "maybe" future, but on current reality.
> Microsoft already accounts for an estimated 60-70% of global cloud gaming services and has other important strengths in cloud gaming from owning Xbox, the leading PC operating system (Windows) and a global cloud computing infrastructure (Azure and Xbox Cloud Gaming).
Microsoft already has a majority of the market. CMA asked Microsoft to provide guarantees they wouldn't abuse their position if they also owned Activision/Blizzard, and whatever guarantees Microsoft provides weren't enough to convince CMA.
> Microsoft’s proposal contained a number of significant shortcomings connected with the growing and fast-moving nature of cloud gaming services:
> It did not sufficiently cover different cloud gaming service business models, including multigame subscription services.
> It was not sufficiently open to providers who might wish to offer versions of games on PC operating systems other than Windows.
> It would standardise the terms and conditions on which games are available, as opposed to them being determined by the dynamism and creativity of competition in the market, as would be expected in the absence of the merger.
Basically, Microsoft tried to weasel their way through the merger so they can prevent other actors from competing with them on a level playing field. Exactly the kind of shit CMA should block.
The conclusion:
> Accepting Microsoft’s remedy would inevitably require some degree of regulatory oversight by the CMA. By contrast, preventing the merger would effectively allow market forces to continue to operate and shape the development of cloud gaming without this regulatory intervention.
Paraphrased: "Either we have to keep close track of them if merger is accepted, or we can just let companies compete in the market"